1. Field of the Invention
The present invention relates generally to audio processing, and more particularly to a noise suppression processing of an audio signal.
2. Description of Related Art
Currently, there are many methods for reducing background noise in an adverse audio environment. A stationary noise suppression system suppresses stationary noise, by either a fixed or varying number of dB. A fixed suppression system suppresses stationary or non-stationary noise by a fixed number of dB. The shortcoming of the stationary noise suppressor is that non-stationary noise will not be suppressed, whereas the shortcoming of the fixed suppression system is that it must suppress noise by a conservative level in order to avoid speech distortion at low signal-to-noise ratios (SNR).
Another form of noise suppression is dynamic noise suppression. A common type of dynamic noise suppression systems is based on SNR. The SNR may be used to determine a suppression value. Unfortunately, SNR by itself is not a very good predictor of speech distortion due to the presence of different noise types in the audio environment. Typically, speech energy, over a given period of time, will include a word, a pause, a word, a pause, and so forth. Additionally, stationary and dynamic noises may be present in the audio environment. The SNR averages all of these stationary and non-stationary speech and noise components. There is no consideration in the determination of the SNR of the characteristics of the noise signal—only the overall level of noise.
To overcome the shortcomings of the prior art, there is a need for an improved noise suppression system for processing audio signals.